Gamma-hydroxybutyrate (GHB), also known as “oxybate,” is an endrogenous compound with hypnotic properties that is found in many human body tissues. GHB is present, for example, in the mammalian brain and other tissues. In the brain, the highest GHB concentration is found in the hypothalamus and basal ganglia and GHB is postulated to function as a neurotransmitter (See Snead and Morley, 1981, Brain Res. 227(4): 579-89). The neuropharmacologic effects of GHB include increases in brain acetylcholine, increases in brain dopamine, inhibition of GABA-ketoglutarate transaminase and depression of glucose utilization but not oxygen consumption in the brain. GHB treatment substantially reduces the signs and symptoms of narcolepsy, i.e., daytime sleepiness, cataplexy, sleep paralysis, and hypnagogic hallucinations. In addition, GHB increases total sleep time and REM sleep, and it decreases REM latency, reduces sleep apnea, and improves general anesthesia (see, e.g., U.S. Pat. Nos. 6,472,431; 6,780,889; 7,262,219; 7,851,506; 8,263,650; and 8,324,275; each of which is incorporated herein by reference in its entirety).
Sodium oxybate (Na⋅GHB), commerically sold as Xyrem®, is approved for the treatment of excessive daytime sleepiness and cataplexy in patients with narcolepsy. Na⋅GHB has also been reported to be effective for relieving pain and improving function in patients with fibromyalgia syndrome (See Scharf et al., 2003, J. Rheumatol. 30: 1070; Russell et al., 2009, Arthritis. Rheum. 60: 299), and in alleviating excessive daytime sleepiness and fatigue in patients with Parkinson's disease, improving myoclonus and essential tremor, and reducing tardive dyskinesia and bipolar disorder (See Ondo et al., 2008, Arch. Neural. 65: 1337; Frucht et al., 2005, Neurology 65: 1967; Berner, 2008, J. Clin. Psychiatry 69: 862).
Xyrem®, for use with patients with narcolepsy, is a chronically used product which requires high levels of the drug. The amount of sodium intake from the drug significantly increases the dietary sodium intake for patients, which is undesirable for patients with hypertension, heart disease, renal disease or at risk of stroke. Further, despite a general record of safety when used as prescribed, there are risks of abuse and misuse of Xyrem® which can cause serious medical problems, including seizures, loss of consciousness, coma, and death (see, e.g., FDA product label dated Nov. 13, 2006 for NDA no. 021196).
Little research has been done on salts of GHB, other than Na⋅GHB, and we are not aware of any combining multiple salts (see, e.g., U.S. Pat. Nos. 4,393,236; 4,983,632; 6,472,431; Ferris and Went, 2012, Forensic Science International 216: 158-162).
Thus, there is a need for GHB formulations that minimize the undesirable side effects of the sodium, particularly in patients with hypertension, heart disease, renal disease or at risk of stroke, yet provide additional health benefits from the presence of the other salts. It is desirable that such modified formulations provide good solubility, stability and purity in order to provide safe, effective and consistent doses to patients, and also display acceptable pharmacodynamic and pharmacokinetic properties.